Optical sensor and method of operation

ABSTRACT

A multiple single use optical sensor includes a series of continuous sensor stripes deposited on a substrate web. At least one sample chamber is adapted to extend transversely across a discrete portion of the series of sensor stripes to facilitate analysis of a sample disposed therein. The sample chamber may be moved, or additional sample chambers provided to enable subsequent measurements of additional samples at unused discrete portions of the sensor stripes. The continuous nature of the sensor stripes provides consistency along the lengths thereof to enable calibration data obtained from one discrete portion of the sensor stripes to be utilized for testing an unknown sample an other discrete portion of the sensor stripes. This advantageously eliminates the need for any particular discrete portion of the sensor stripes to be contacted by more than one sample, for improved sensor performance.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to chemical analysis of liquids, and moreparticularly, to an optical sensor for sensing analyte content ofbiological fluids such as blood.

[0003] 2. Background Information

[0004] Chemical analysis of liquids, including biological fluids such asblood, plasma or urine is often desirable or necessary. Sensors thatutilize various analytical elements to facilitate liquid analysis areknown. These sensing elements have often included a reagent in either awet or dry form sensitive to a substance or characteristic underanalysis, termed analyte herein. The reagent, upon contacting a liquidsample containing the analyte, effects formation of a colored materialor another detectable change in response to the presence of the analyte.Examples of dry analytical sensing elements include pH test strips andsimilar indicators wherein a paper or other highly absorbent carrier isimpregnated with a material, chemically reactive or otherwise, thatresponds to contact with liquid containing hydrogen ion or other analyteand either generates color or changes color. Specific examples of suchtest strips are disclosed in European publication No. EP 0119 861 B1,which describes a test for bilirubin; in U.S. Pat. No. 5,462,858 whichdescribes a dry multilayer strip for measuring transaminase activity;and U.S. Pat. No. 5,464,777 which discloses a reflectance based assayfor creatinine. While providing a convenience factor, in that they canbe stored dry and are ready to use on demand, these individual testelements are generally utilized in “wet” blood or serum chemistry,wherein the strips become saturated during use. This hydration and thedepletion of reactive chemical reagents effectively prevents theirre-use. This aspect also complicates handling and disposal of themultitude of individual used test elements.

[0005] Alternatively, some analytes can be measured with a sensingelement which is used repeatedly after an initial wet-up and calibrationand with washes between samples. For example a reuseable electrochemicalsensor for oxygen is described in commonly assigned U.S. Pat. No.5,387,329 and a reuseable electrochemical sensor for glucose isdescribed in commonly assigned U.S. Pat. No. 5,601,694. These sensorsfunction within the context of a complex piece of supportinstrumentation to perform the repetitive calibration and washfunctions.

[0006] Other analytical sensing elements which are based on an opticalsignal response are disclosed in U.S. Pat. Nos. 4,752,115; 5,043,286;5,453,248 and by Papkovsky et al in Anal. Chem. vol 67 pp 4112-4117(1995) which describe an oxygen sensitive dye in a polymer membrane, asdoes commonly assigned U.S. patent application Ser. No. 08/617,714,which is hereby incorporated in its entirety, herein. Examples of anoptical CO₂ sensor are described in U.S. Pat. Nos. 4,824,789; 5,326,531and 5,506,148. These elements utilize a polymer based membrane chemistryto achieve advantages in storage, and continuous use or re-use ascompared to the wetable or hydrated single use chemistry strips.Analytical elements of this type are typically adapted for multiple useswithin a single sample chamber of an optical sensor assembly. Inoperation, a fluid sample of unknown analyte content (an “unknownsample”) is tested by inserting the sample into the sample chamber whereit contacts the analytical element. A change in the optical propertiesof the analytical element is observed. Such an observation is thencompared to calibration data previously obtained by similarly testing acalibration liquid of known analyte content. In this manner,characteristics of the analyte of interest in the unknown sample aredetermined.

[0007] An example of a single use optical sensor application of thisnormally reuseable type is known as a “AVL OPTI 1” available from AVLList GmbH of Graz, Austria. While sensors of this type may operatesatisfactorily in many applications, they are not without limitations.In particular, they rely on sequential steps for calibration andsubsequent sample readings, in which each such sensing device must beindividually calibrated prior to testing an unknown sample. Thistechnique is required due to variations in analytical elements fromsensor to sensor. These variations may be attributed to a variety offactors, including manufacturing variables such as differences inindividual lots, and distinct storage histories.

[0008] Sequential calibration and sample reading may problematicallylead to sample contamination in the event the sample chamber andanalytical elements are insufficiently washed between samples. Inaddition, the calibration is time consuming and may delay analysis ofthe unknown sample. This delay may be particularly inconvenient in someoperating environments such as, for example, critical care facilities.

[0009] An additional disadvantage of the sequential approach is thetemporal variation or time delay between testing of the calibrant andtesting of the unknown sample. This variation may provide a potentialopportunity for inaccuracies in test results.

[0010] Further, discarded wash fluid comprises approximately 80% of thewaste generated by such conventional sensor based testing techniques.This waste is classified as biohazardous particularly if it isco-mingled with biological samples and thus disposal thereof isrelatively expensive, both in economic and environmental terms. Thiswaste also poses a potential health risk to health care workers andthose who may otherwise come into contact with the waste during or afterdisposal.

[0011] Thus, a need exists for an improved optical sensor thateliminates the need for serial calibration and addresses the problems ofwaste generation inherent in sensor practices of the prior art whileretaining the advantages of disposable, use on demand, devices.

SUMMARY OF THE INVENTION

[0012] According to an embodiment of the present invention, an opticalsensor adapted for sensing analyte content of a plurality of samples isprovided. The optical sensor comprises:

[0013] a substrate web of predetermined length, the substrate web beingsubstantially gas impermeable and optically transparent in apredetermined spectral range;

[0014] a plurality of elongated sensor stripes extending in a parallelspaced relation along the length of the web;

[0015] each one of the plurality of sensor stripes adapted for providingan optically discernible response to presence of at least one analyte;

[0016] the optical sensor adapted for selective analyte-sensing contactwith the plurality of samples, wherein each one of the plurality ofsamples are selectively superimposable with each one of the plurality ofelongated sensor stripes at one of a plurality of discrete positionsalong the lengths thereof;

[0017] the optically discernible response being substantially identicalat a plurality of discrete positions along the length thereof.

[0018] In a first variation of this aspect of the present invention, anoptical sensor assembly adapted for sensing analyte content of aplurality of samples is provided. The optical sensor assembly comprises:

[0019] the optical sensor as set forth in the above-referenced firstaspect of the present invention;

[0020] at least one sample chamber selectively superimposable with eachof the plurality of elongated sensor stripes at the plurality ofdiscrete positions along the lengths thereof;

[0021] wherein the at least one sample chamber is adapted foralternately maintaining individual ones of the plurality of samples inthe analyte-sensing contact.

[0022] In a second variation of the first aspect of the presentinvention, an optical sensor assembly adapted for sensing analytecontent of a plurality of samples is provided. The optical sensorassembly includes:

[0023] the optical sensor as set forth in the above-referenced firstaspect of the present invention;

[0024] a plurality of sample chambers disposed in parallel, spacedrelation on the web, each one of the plurality of sample chambers beingsealably superposed with the plurality of elongated sensor stripes atone of a plurality of discrete positions along the lengths thereof;

[0025] wherein each of the plurality of sample chambers is adapted foralternately maintaining individual ones of the plurality of samples inthe analyte-sensing contact.

[0026] In a second aspect of the present invention, a method ofoperating an optical sensor comprises the steps of:

[0027] (a) providing an optical sensor including:

[0028] i) a substrate web of predetermined length, the substrate webbeing substantially gas impermeable and optically transparent in apredetermined spectral range;

[0029] ii) a plurality of elongated sensor stripes extending inparallel, spaced relation along the length of the web, each one of theplurality of sensor stripes adapted for providing an opticallydiscernible response to presence of at least one of a plurality ofdiscrete analytes;

[0030] iii) the optical sensor adapted for selective analyte-sensingcontact with the plurality of samples, wherein each one of the pluralityof samples are selectively superimposable with each one of the pluralityof elongated sensor stripes at one of a plurality of discrete positionsalong the lengths thereof;

[0031] iv) the optically discernible response being substantiallyidentical at a plurality of discrete positions along the length thereof;

[0032] v) wherein the plurality of samples comprises at least oneunknown sample and at least one calibration sample, the optical sensoradapted for being calibrated upon disposition of the calibration samplein the analyte-sensing contact with the optical sensor at a discreteposition along the length of the sensor stripes distinct from that ofthe at least one unknown sample;

[0033] (b) placing the calibration sample in the analyte-sensing contactwith the optical sensor at one of the plurality of discrete positionsalong the lengths of the sensor stripes;

[0034] (c) measuring optical response of the optical sensor at the oneof the plurality of discrete positions;

[0035] (d) obtaining calibration data utilizing the optical response ofthe one of the plurality of discrete positions;

[0036] (e) placing the at least one unknown sample in theanalyte-sensing contact with the optical sensor at an other of theplurality of discrete positions along the lengths of the sensor stripes;

[0037] (f) measuring optical response of the other of the plurality ofdiscrete positions;

[0038] (g) utilizing the calibration data obtained for the one of theplurality discrete positions for calibration of the optical response ofthe other of the plurality of discrete positions.

[0039] The above and other features and advantages of this inventionwill be more readily apparent from a reading of the following detaileddescription of various aspects of the invention taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0040]FIG. 1 is a plan view of an optical sensor of the presentinvention;

[0041]FIG. 2 is a perspective view of an embodiment of an optical sensorassembly of the present invention, including the optical sensor of FIG.1 and a sample chamber disposed thereon;

[0042]FIG. 3 is a cross-sectional elevational view taken along FIG. 3-3of FIG. 2;

[0043]FIG. 4A is a perspective view, with portions thereof peeled back,of an alternate embodiment of an optical sensor assembly of the presentinvention, including the optical sensor of FIG. 1 and a plurality ofsample chambers disposed thereon;

[0044]FIG. 4B is a view similar to FIG. 4A, of another alternateembodiment of an optical sensor assembly of the present invention;

[0045]FIG. 4C is a view similar to FIGS. 4A and 4B, of a furtheralternate embodiment of an optical sensor assembly of the presentinvention;

[0046]FIG. 5 is a schematic representation of a portion of a testapparatus capable of use in combination with an optical sensor of thepresent invention;

[0047]FIG. 6 is a schematic representation of a test apparatus includingthe portion thereof shown in FIG. 5, capable of measuring the outputsignal of a luminescent optical sensor of the present invention;

[0048]FIG. 7A is a graphical representation of optical response of aportion of an optical oxygen sensor of the type shown in FIGS. 1 and 4;

[0049]FIG. 7B is a graphical representation of response to aqueousbuffer samples, of the portion of the optical oxygen sensor utilized togenerate FIG. 7A;

[0050]FIG. 8 is a graphical representation of the response of an opticaloxygen sensor of the type shown in FIGS. 1 and 4 and constructed from asecond different membrane and dye formulation;

[0051]FIG. 9 is a response curve similar to that of FIG. 7B, for acarbon dioxide sensing portion of an optical sensor of the type shown inFIGS. 1 and 4;

[0052]FIG. 10 is a graphical representation of response to acidificationof the fluorescein dye, of the portion of the optical pH sensordescribed in FIGS. 1 and 4;

[0053]FIG. 11 is a graphical representation of the simultaneous responseof sensors of the present invention, for three analytes, for threedifferent known samples; and

[0054]FIG. 12 is a graphical response curve for a single oxygen sensorstripe of the present invention calibrated by the use of several knownsamples similar to those utilized to generate FIG. 11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0055] Referring to the figures set forth in the accompanying drawings,illustrative embodiments of the present invention will be described indetail hereinbelow. For clarity of exposition, like features shown inthe accompanying drawings shall be indicated with like referencenumerals and similar features shown, for example, in alternateembodiments in the drawings, shall be indicated with similar referencenumerals.

[0056] Briefly described, the present invention includes a multiplesingle use optical sensor fabricated as a series of continuous sensorstripes 14 deposited on a substrate web 12 (FIG. 1). One sample chamber16 (FIG. 2) or multiple sample chambers 116 (FIG. 4) are adapted toextend transversely across a discrete portion of the series of sensorstripes 14 to facilitate analysis of a sample disposed therein. Samplechamber 16 may be moved, or additional sample chambers utilized toenable subsequent measurements of additional samples at unused discreteportions of sensor stripes 14. The continuous nature of the sensorstripes provides consistency along the lengths thereof to enablecalibration data obtained from one discrete portion of a sensor stripe14 to be utilized for testing and determining presence and concentrationof analytes in an unknown sample disposed at an other discrete portionof the sensor stripe. This aspect advantageously eliminates the need forany particular discrete portion of a sensor stripe 14 to be contacted bymore than one sample for improved sensor performance and reduced waste.

[0057] Throughout this disclosure, the term “analyte” shall refer to anysubstance, compound, or characteristic such as, for example, pH, capableof detection and/or measurement relative to a liquid sample. Similarly,the term “concentration” shall refer to the level or degree to which ananalyte is present in a sample. The term “axial” or “longitudinal” whenused in reference to an element of the present invention, shall refer tothe relatively long dimension or length thereof. For example, when usedin connection with an optical sensor of the present invention,“longitudinal” shall refer to a direction substantially parallel tosensor stripes 14 thereof. Similarly, the term “transverse” shall referto a direction substantially orthogonal to the axial or longitudinaldirection. Moreover, the use of the term “calibration” or “calibrationsample” shall be understood to encompass a sample of substantially anyknown analyte composition, including “QC” or “quality control” samplescommonly used by those skilled in the art to help ensure uniformitybetween tests.

[0058] Referring now to the drawings in detail, as shown in FIG. 1, anoptical sensor 10 of the present invention includes a backing orsubstrate web 12, with a plurality of sensor stripes 14 extendinglongitudinally in parallel, spaced relation thereon. Backing web 12 isfabricated as a sheet from a material optically transparent in apredetermined optical spectrum, as will be discussed hereinafter. Thebacking web is preferably fabricated from a substantially liquid and gasimpermeable material, such as, for example, glass or a thermoplasticmaterial such as polyethylene terephthalate or SARAN®.

[0059] In this regard, those skilled in the art will recognize thatfabrication of the substrate web from relatively gas permeablematerials, such as, for example, Polytetrafluoroethylene (PTFE), maydisadvantageously distort analyte analysis. This is due to the tendencyfor analytes to diffuse out of the sample, or for ambient gases such asatmospheric Oxygen (O₂) and/or Carbon Dioxide (CO₂), to leach out of thesubstrate and into the sensor material and sample, during analysis. In apreferred embodiment, substrate web 12 is fabricated as a film ofpolymeric plastic material sold under the Dupont trademark Mylar®. Webswere obtained from ERA Industries INC. in Seabrook N.H. In addition tobeing substantially gas impermeable, this material advantageouslyprovides substrate web 12 with flexibility, as will be discussed ingreater detail hereinafter. The substrate web may be fabricated usingany convenient method common in the art, such as conventional molding,casting, extrusion or other suitable thin-film fabrication techniques.

[0060] Each sensor stripe 14 may be fabricated as a series of discreteportions, such as a series of dots, arranged in a row extendinglongitudinally along the substrate web. Alternatively, in a preferredembodiment as shown, each sensor stripe 14 extends substantiallycontinuously in the longitudinal direction. Each sensor stripe 14comprises at least one of any number of analytical elements, includingsubstances, compounds or structures known to those skilled in the art tobe optically sensitive to a predetermined analyte. Such opticalsensitivity may include, for example, exhibition of opticallydiscernible changes in reflectance, refractive index, lighttransmittance, or in a preferred embodiment, luminescence, which mayencompass emitted light in the form of either phosphorescence orfluorescence.

[0061] Examples of analytes that may be analyzed include BUN (blood ureanitrogen), glucose, calcium (Ca⁺⁺), potassium (K⁺), sodium (Na⁺), pH,and partial pressures of carbon dioxide (pCO₂) and oxygen (pO₂).Preferred analytical elements include, for example, analytical elementsfor carbon dioxide (pCO₂) as disclosed in U.S. Pat. Nos. 5,387,525 (the'525 patent) and 5,506,148 (the '148 patent), an analytical element forpH as disclosed in International Publication No. WO 95/30148 and byBruno, et al. in Anal. Chem. Vol 69, pp. 507-513 (1997) and ananalytical element for oxygen (pO2) as disclosed in U.S. patentapplication Ser. No. 08/617,714, all of which are hereby incorporated byreference in their entireties, herein. All of these preferred analyticalelements emit characteristic luminescence which is responsive to thepresence of their respective analytes when subjected to incident lightof a predetermined spectral wavelength or spectral range.

[0062] In a preferred embodiment, each sensor stripe 14 comprises asingle analytical element. However, it is contemplated that a singlesensor stripe of the present invention may comprise a plurality ofanalytical elements, each of the plurality of analytical elementsexhibiting an independently measurable response to presence of theirrespective analytes. In this regard, for example, a single sensor stripe14 may comprise first, second and third analytical elements. The firstanalytical element may exhibit enhanced fluorescence in presence of afirst analyte when subjected to incident light in a first spectralrange. The second analytical element may exhibit diminishedphosphorescence in presence of a second analyte when subjected toincident light in a second spectral range. The third analytical elementmay, for example, exhibit another optical response, such as enhancedreflectance, in presence of a third analyte when subjected to incidentlight in a predetermined spectral range.

[0063] Sensor stripes 14 are applied to the substrate web 12 by anyconvenient means, either by batch or continuous processes. For example,stripes 14 may be applied by conventional printing techniques, such assilk screen or other lithographic techniques. It is also contemplatedthat laser or ink jet printing technologies may ultimately be adaptedfor application of the sensor stripes. Alternatively, the stripes may beapplied by continuous direct deposition or painting-type applicationtechniques as well as by spray painting.

[0064] For example, in a preferred embodiment, one may use a microdispensing system of the type commercially available from Gilson,Worthington, Ohio; Cavro Scientific Instruments Inc., Sunnyvale, Calif.;Elder Laboratories Inc., Napa, Calif.; IVEK Corp., Springfield, Vt.; orFluid Metering Inc., Oyster bay, N.Y., as well as other commercialsources for chromatographic delivery systems. Operation of thisequipment is familiar to those of skill in the art. Briefly described,the material comprising the sensor stripe, including at least oneanalytical element, is prepared in liquid form and fed to a nozzle ofpredetermined size and shape, suspended or superposed over substrate web12. The liquid is expressed from the nozzle at a predetermined rate ontothe substrate web as the web is moved longitudinally at a predeterminedrate relative the nozzle with either reciprocating or rolled webtechnologies of a more continuous nature. This process is repeated atspaced locations along the transverse dimension or width of thesubstrate web for each sensor stripe. The liquid is then dryed or curedin a conventional manner to form a solid sensor stripe 14.

[0065] While the aforementioned method for deposition of sensor stripes14 is preferred, substantially any method of deposition may be utilizedthat enables the mechanical and optical properties of sensor stripes 14to be held substantially constant over the lengths thereof. In thisregard, parameters such as stripe thickness, width, contour, andcomposition are maintained at predetermined levels to provide sensorresponse that is relatively constant or identical at various positionsalong the length of each sensor stripe 14. Moreover, the skilled artisanwill recognize that sensor response will be particularly consistent overrelatively short sections of the stripe. In other words, the uniformityof response of discrete portions of a sensor stripe 14 will be in somemeasure proportional to the spatial distance therebetween.

[0066] Referring now to FIG. 2, an optical sensor assembly 15 of thepresent invention includes a sample chamber 16 adapted for use incombination with optical sensor 10. Sample chamber 16 comprises anelongated, substantially tubular cavity 18 disposed within an elongatedchamber member 19. Cavity 18 has a transverse cross-section nominallyuniform along the length thereof and defined, in part, by asubstantially concave or recessed surface 21, best shown in FIG. 3.Throughout this disclosure, the term “concave” shall refer to anysubstantially hollowed out recess or cavity, regardless of whether thesurface thereof is curved or comprises a plurality of substantially flatsurfaces as shown herein. In this regard, referring to FIG. 3, concavesurface 21 extends inwardly from a substantially planar engagementsurface 24 of chamber member 19.

[0067] As shown in FIGS. 2 and 3, engagement surface 24 is adapted forbeing superimposed transversely across, preferably in slidable,surface-to-surface engagement with substrate web 12 and sensor stripes14. So disposed, a discrete portion of web 12, including portions ofsensor stripes 14, effectively closes concave surface 21, to thus definea longitudinal side wall of tubular cavity 18. Moreover, engagementsurface 24, substrate web 12 and sensor stripes 14 are each sufficientlysmooth that upon application of a predetermined force tending tomaintain such surface-to-surface contact, a fluid-tight seal ismaintained therebetween. Sample chamber 16 is thus adapted forsupportably maintaining a fluid sample in surface to surface oranalyte-sensing contact with a discrete portion of each sensor stripe14, as will be discussed in greater detail hereinafter with respect tooperation of the embodiments of the present invention.

[0068] As shown in FIG. 2, entry and exit apertures 20 and 22,respectively, each extend through chamber member 19. The apertures eachextend orthogonally to, and in communication with, cavity 18 at oppositeends thereof, to facilitate sample flow into and out of sample chamber16.

[0069] As shown, sample chamber 16 is a reusable device, adapted foreither multiple tests at a particular discrete location on sensorstripes 14, or alternatively, progressive movement to fresh (unused)portions of the sensor stripes for successive sample testing. Thesealternative testing techniques will be discussed hereinafter withrespect to operation of the present invention.

[0070] Referring now to FIG. 4A, an alternate embodiment of the presentinvention is shown as optical sensor assembly 115. This optical sensorassembly includes multiple individual sample chambers 116 disposed onoptical sensor 10. Sensor assembly 115 is preferably fabricated as alaminate comprising optical sensor 10, an intermediate or chamber web 26and a cover web 28.

[0071] Chamber web 26, in combination with cover web 28, comprise samplechambers 116. As shown, chamber web 26 is an elongated sheet thatincludes a series of transversely extending cavities 118. The cavitiesare spaced at predetermined distances from one another along the lengthof the web.

[0072] Web 26 is preferably fabricated from a material and in a mannersimilar to that of substrate web 10. Cavities 118 are formed by anyconvenient method, such as, for example, by subjecting web 26 toconventional die-cutting operations. Alternatively, in the event web 26is fabricated by molding, cavities 118 may be molded integrallytherewith.

[0073] Cover web 28 is superimposed or laminated in a sealed,fluid-tight manner over chamber web 26. This combination of chamber web26 and cover web 28 effectively provides each chamber 116 with atransverse cross-section defined by concave surface 21 as describedhereinabove with respect to FIG. 3. A series of entry and exit bores orapertures 20 and 22 extend through cover web 28 in communication withopposite ends of cavities 118 as also discussed hereinabove.Alternatively, the bores or apertures 20 and 22 may also be formed inthe substrate web itself 12 or used in combination with apertures in thecover web 28. Cover web 28 is preferably fabricated from a material andin a manner similar to that of both substrate web 12 and chamber web 26.Any conventional means, including, for example, ultrasonic and vibrationwelding or adhesives of various types may be utilized to laminate coverweb 28 to chamber web 26. In a preferred embodiment, however, aconventional adhesive is utilized to bond webs 26 and 28 to one another.

[0074] Chamber web 26 is laminated onto optical sensor 10 so that sensor10 effectively closes and seals concave surfaces 21 of each cavity 118in a manner similar to that described hereinabove with respect to cavity18. Thus, rather than being movable as is cavity 18 describedhereinabove, cavities 118 are preferably immovably or permanentlydisposed at spaced intervals along the length of optical sensor 10. Themanner in which chamber web 26 is laminated onto optical sensor 10 issimilar to that in which chamber web 26 is bonded to cover web 28.

[0075] Turning now to FIG. 4B, a further alternate embodiment is shownas optical sensor assembly 115′. Assembly 115′ is substantially similarto optical sensor assembly 115, with the distinction that entry and exitapurtures 20′ and 22′ are disposed in substrate web 12, rather than inweb 28.

[0076] An additional, similar alternative embodiment is shown in FIG. 4Cas optical sensor assembly 115″. In assembly 115″, some of the entry andexit apertures (i.e. exit apertures 22 as shown) are disposed in web 28while others of the entry and exit apertures (i.e. entry apertures 20′)are disposed in substrate web 12.

[0077] Preferred embodiments of the invention having been described, thefollowing is a description of the operation thereof. Referring initiallyto optical sensor assembly 15, as shown in FIGS. 2 and 3, a sample to betested is inserted into entry aperture 20, such as by a pump means (notshown but which may include the use of capillary forces or negative orpostive pressures). The sample is inserted until it substantially fillssample chamber 16 and is thus placed in analyte-sensing contact with adiscrete portion of each respective sensor strip 14 as discussedhereinabove. Once so disposed, any of a variety of suitable instrumentsmay be utilized to measure optical response of the discrete portions todetermine the existence and/or concentration of analytes in the sample.Examples of such instrumentation include a commercially availablefluorimetric device known as a model LS50-b Spectrofluorimeter availablefrom Perkin Elmer Corporation of Norwalk, Conn. A solid sample holderaccessory was specifically modified to accept the striped film sensorsfor front face fluorescence measurements. By “front face” or “frontsurface” it is meant that excitation and emission collection is off thesame surface. Illumination and collection optics permit transmission ofthe excitation and emission signals through the Mylar® substrate.Samples were introduced into a hollowed out aluminum sample chamberlocated on the side of the Mylar® opposite from the illumination andcollection optics and with the opening covered by the sensor stripe sothat samples contacted the stripe directly. Sample measurements withthis device are provided in Example 6 (FIG. 9) and Example 8 (FIG. 10).

[0078] Alternatively, a test apparatus 140 as depicted in FIG. 5 may beutilized. Briefly described, such an apparatus 140 includes a flow cellassembly 60 and an excitation source and detector sub-system 100 such asthat disclosed in U.S. patent application Ser. No. 08/617,714, and whichis incorporated by reference in its entirety herein. Sub-system 100emits a beam of light having a predetermined wavelength or spectralrange. The light is directed through fiber optic cable 80 onto thesurface of substrate web 10 directly opposite a stripe 14 in samplechamber 16. The light passes through the web, which, as mentionedhereinabove, is substantially transparent thereto, wherein the light isincident on a predetermined one of the sensor stripes 14. The incidentlight serves to excite a portion of sensor stripe 14. Stripe 14 thenexhibits an optical response that corresponds to parameters (e.g.presence and/or concentration) of the predetermined analyte in thesample disposed in the sample chamber. This optical response is receivedby detector sub-system 100.

[0079] The calibration information for the optical sensor assembly isobtained by inserting a calibration sample or calibrant of known analytecomposition into the sample chamber and measuring response of the sensorstripes thereto, in a manner substantially similar to testing an unknownsample.

[0080] Referring now to FIGS. 5 and 6, test apparatus components 60 and100 are described in additional detail. As shown in FIG. 5, flow cellassembly 60 is adapted to receive an optical sensor 10 for measurement.Radiation or light impinging upon substrate web 12 and emitted fromstripe 14 is respectively guided to and from source and detectionsub-system 100 by a fiber optic cable 80. Cable 80 includes a core 82,cladding 84 and sheath 86 where the core 82 and cladding 84 may beconstructed from either glass or plastic polymer materials. Cable 80 isimbedded into base 62 which preferably has a low permeability to gasesand a flat surface for contact with substrate 12. Base 62 may comprisestainless steel or another hard, thermally conductive material which iscapable of assisting in controlling the temperature of membrane 14.Source radiation from cable 80 passes through substrate 12 and excitesthe luminescent dye molecules dispersed within membrane 14. Elongatedmember 19, including sample chamber 16, is pressed flat against opticalsensor 10 as discussed hereinabove. Alternatively, optical sensorassembly 115 (FIG. 4), including sample chambers 116 (FIG. 4) may beutilized. Samples may be entered and subsequently removed through theentrance and exit apertures 20 and 22. The signal from each individualstripe 14 is then transmitted by cable 80 and returned to source anddetector sub-system 100.

[0081] Referring to FIG. 6, the measurement apparatus 140 is comprisedof flow cell assembly 60 and source and detector subsystem 100. For theoptical source and detector sub-system 100 an LED source 152, and lens154 are used to launch excitation light through filter 162 into one leg182 of the fiber optic splitter 180 (avilable from American LaubscherCorp., Farmingdale, N.Y.). The luminescent or emitted light signalreturning from the sensor 10 down fiber cable 80 and leg 184 is passedthrough filter 168 and aperture 158 before detection by photodiode 172.The output current of emission detector 172 is amplified with apreamplifier 174, such as a Stanford Research SR570 currentpreamplifier, converted to a voltage and recorded for use in analysis.For example, with the pH sensing dye fluorescein used in a sensorstripe, a Panasonic®Blue LED (P389ND available from Digikey, Theif RiverFalls, Minn.) would be preferred for source 152. A 485 nm centerwavelength 22 nm half bandwidth filter (available from Omega Optical,Brattleboro, Vt.) would be preferred for filter 162 and a 535 nm centerwavelength 35 nm half bandwidth filter, also available from OmegaOptical, Brattleboro, Vt. would be preferred for filter 168. It shouldalso be evident that each individual sensor stripe, employing adifferent dye, will require its own preferred LED source 152, excitationinterference filter 162 and emission interference filter 168. Whileparticular arrangements of optical source and detection systems havebeen disclosed herein, other equivalent instruments are known to thoseskilled in the art and are intended to be within the scope of thepresent invention.

[0082] Testing procedures are undertaken at each sensor stripe 14 insample chamber 16, either sequentially or in parallel, to test for allof the predetermined analytes. Once analysis is complete, the pump meansremoves the sample from chamber 16 through exit aperture 22.

[0083] Analysis of subsequent samples, as well as the aforementionedanalysis of a calibration sample, may be accomplished in a manner commonto prior art sensors. Namely, sample chamber 16 may be flushed with washfluid to remove traces of the previous sample from the sample chamberand sensor stripes. Sample chamber 16 and the same discrete portions ofsample stripes 14 with which the sample chamber is superposed, may bere-used for a subsequent test sample. In this manner, sensor assembly 15may function as a conventional ‘multiple use’ device. Alternatively thepresent invention includes use of optical sensor 10 as a ‘multiplesingle use device’ in which subsequent tests may be performed atdiscrete unused portions of sensor stripes 14. In this regard, aftertesting is completed, sample chamber 16 may be washed and driedsufficiently to clear any sample traces from chamber member 19 andprevent liquid carryover to the next chosen position. Sample chamber 16may then be moved relative the length of optical sensor 10 tosuperimpose cavity 18 with an unused portion of sensor stripes 14. Onceso disposed, a subsequent sample may be fed into sample chamber 16 foranalyte analysis. These steps may be reiterated, so that a freshdiscrete portion of each sensor stripe 14 is used for each sample(calibrant or unknown) in either a sequential or simultaneous manner.

[0084] However, the present invention is preferably used in the‘multiple single use’ mode when it is combined with provisions for aplurality of sample chambers 116, as shown in FIG. 4, to enable eachsample chamber to be used only once. This nominally eliminates the needfor washing operations and each sample chamber effectively becomes awaste container for its own sample. In addition, this aspectsubstantially eliminates the potential for cross-contamination ofsamples occasioned by repeated use of sample chambers, as mentionedhereinabove.

[0085] An additional advantage of this construction is the ability toconduct parallel testing of unknown and calibration samples. In thisregard, sample chambers 116 disposed proximate, and preferably adjacent,one another may be utilized for simultaneously testing calibrationsamples and unknown samples. Such parallel, simultaneous testingprovides additional precision in testing not available with prior artdevices by effectively eliminating any inaccuracies in sensor responseoccasioned by temporal variations between tests of calibration andunknown samples.

[0086] Moreover, in a further variation, both sensor assembly 15 (FIG.2) and sensor assembly 115 (FIG. 4) may be calibrated at multiplediscrete positions along the lengths of sensor stripes 14. Thisadvantageously provides additional data points for increased precisionof the calibration information. In this regard, for still furtherprecision, calibration samples may be tested in chambers disposed onopposite sides of, and adjacent to, a sample chamber containing anunknown sample.

[0087] This multiple position calibration also facilitates utilizationof discrete calibration samples having different combinations ofanalytes disposed therein. This aspect tends to enhance the stability ofthe individual calibration mixtures by enabling separation of analytes,such as, for example, glucose and oxygen. One skilled in the art willrecognize that the presence of oxygen in a glucose solution tends tofavor oxidative microorganism growth. Thus, it is advantageous to haveseparate oxygen and glucose calibration solutions. In general, a firstcalibration sample may be provided with a first predeterminedcombination of analytes, and a second calibration sample provided with asecond predetermined combination of analytes. The first and secondcalibration samples then may be tested simultaneously at discretepositions of sensor stripes 14. The data obtained from testing theseseparate calibration samples may be combined for analyzing test resultsfor unknown samples at the same or other discrete positions along sensorstripes 14.

[0088] Thus, as discussed hereinabove, rather than rely on temporalstability, the present invention relies on spatial stability, namely theassumption that sensor portions located proximate one another along thesensor stripes will exhibit substantially identical responsecharacteristics. This reliance is made possible by the deposition of theanalytical elements as substantially continuous sensor stripes 14 asdiscussed hereinabove, with increased precision enabled, as desired,through the use of adjacent sample chambers 116 for respective testingand calibration.

[0089] Moreover, the combination of spatial and temporal proximity inthese measurements permits the use of conventional differential andratiometric techniques to further improve accuracy and precisionthereof. In particular, by introducing and measuring an unknown sampleand a calibrant into respective sample chambers at the same time, it ispossible to simultaneously observe and compare the response dynamics ofthe calibrant versus the unknown sample to further enhance accuracy ofresponse measurement.

[0090] The construction of the present invention also addresses theproblem of storage history variations that tend to compromiseperformance and consistency of prior art sensors. For example, otherwiseidentical prior art sensors may have been stored for different periodsof time or exposed to variations in environmental conditions (e.g.differences in temperature, humidity or radiation) during storage, thatmay impact consistency between sensors. By virtue of fabricating theanalytical elements as nominally continuous stripes on a singlesubstrate, the present invention tends to ensure that each discreteportion of sensor stripes 14 has an identical storage history to furtherimprove sensor consistency.

[0091] Moreover, the present invention, particularly sensor assembly115, provides an additional advantage in terms of waste reduction. Asmentioned hereinabove, approximately 80% of waste in connection withprior art sensors comprises wash fluid used to clean the sample chamberand analytical elements between unknown samples. Such waste is generallyclassified as biohazardous, thus requiring relatively rigorous andexpensive special handling. By substantially reducing or eliminating thewashing requirements through the construction of individualized samplechambers 116 as discussed hereinabove, the present invention effectivelyreduces biohazardous waste relative to prior art devices, for desireablecost and safety improvements.

[0092] The following illustrative examples are intended to demonstratecertain aspects of the present invention. It is to be understood thatthese examples should not be construed as limiting. In the examples,sensor stripes 14 were deposited on a 75 micrometers (m) thick Mylar®substrate web 12 positioned with an IVEK LS Table. Deposition of thepolymer and dye formulations was achieved with a micro dispensing systemof the type discussed hereinabove. Examples of the construction ofstriped sensor membranes and demonstrations of their functionality aregiven in the following:

EXAMPLE 1

[0093] Into one ml of the solvent tetrahydrafuran (THF) from Alrich(Milwaukee, Wis.) were dissolved 100 mg of polystyrene (MW=280,000 andobtained from Scientific Polymer Products Inc. in Ontario, N.Y.) and 2mg of the oxygen sensing dye octaethyl-Pt-porphyrin ketone (OEPK)purchased from the Joanneum Research Institute in Graz Austria. Theviscosity of the solution was 37 centipoise (cps) as measured on aBrookfield RVDVIIIC/P Rheometer. The mixture was then deposited througha nozzle located 75 m above a clear Mylar® film and at a rate of 5ml/sec with a Digispense 2000 pump system from IVEK to produce a stripeat a linear rate of 50 mm/sec, having a width of approximately 2 mm anda thickness of about 5 m when dried. After air drying, the stripes werecured at 110° C. for one hour under a vacuum and cooled to remove alltraces of solvent. The resultant oxygen sensing stripes were translucentand of a light purple color.

EXAMPLE 2

[0094] A sensor stripe from example 1 was placed in the measurementdevice described with respect to FIG. 5 but altered to contain theappropriate yellow LED source, an Omega 585DF20 excitation filter, and aOmega 750DF50 emission filter for the dye octaethyl-Pt-porphyrin ketone.A flowing gas stream with differing partial pressures of oxygencorresponding to 0%, 100%, 26%, 12%, 7%, 12%, 26%, 100% and finally 0%oxygen was passed over the sensor and the luminescence elicited from thedye recorded. The luminescence quenching trace in FIG. 7A was used toderive a Stern-Volmer quenching constant of 0.026 (mmHg)⁻¹. The exposureof the striped oxygen sensing membrane to duplicate aqueous buffersamples tonometered to partial pressures of 92, 43 and 171 mm Hg oxygenalso produced rapid, and reversible responses as documented in FIG. 7Bwhich could be used to quantitate the amount of dissolved oxygen insolution.

EXAMPLE 3

[0095] A sensing stripe for the analyte oxygen was constructed asfollows. The dye octaethyl-Pt-porphyrin was synthesized according tomethods described in J. Molecular Spectroscopy 35:3 p359-375 (1970). Thestyrene/acrylonitrile copolymer, with MW=165,000 and containing 25%acrylonitrile, was obtained from Scientific Polymer Products Inc.,Ontario, N.Y. A mixture of 2 mg dye and 100 mg of copolymer dissolvedinto 1 ml of THF was deposited on a Mylar® film as in example

EXAMPLE 4

[0096] A sensor stripe from example 3 was placed in the measurementdevice described hereinabove with respect to FIG. 5 and a flowing gasstream with differing partial pressures of oxygen corresponding to 0%,26% and finally 100% oxygen were passed over the sensor. Theluminescence elicited with green 540 nm excitation light from theoctaethyl-Pt-porphyrin dye was continuously measured at 650 nm and theluminescence quenching trace recorded as shown in FIG. 8.

EXAMPLE 5

[0097] An analytical element for CO₂ was fabricated substantially as setforth in the above-referenced '525 and '148 patents. Namely, a 7%solution (by weight) of ethyl cellulose was prepared by dissolving 7 gin 100 ml of a 7:3 toluene:ethanol mixture. To this solution was added 5mg of hydroxpyrenetrisulponic acid (HPTS). 2 ml of Tetrabutylamoniumhydroxide was added to the mixture. The solution striped at a linearrate of 50 mm/sec with a solution delivery rate of 5 ml/sec with thenozzle located 75 m above the substrate. After air drying overnight thisproduced very faintly green stripes for CO₂ sensing.

EXAMPLE 6

[0098] A portion of the striped CO₂ sensor in example 5 was placed in anoptical chamber on a Perkin Elmer LS-50B spectrofluorimeter. Frontsurface illumination and collection optics permitted transmission of the460 nm excitation and 506 nm emission signals through the Mylar®substrate. Tonometered liquid samples were introduced into a hollowedout aluminum sample chamber with an opening covered by the sensorstripe. Introduction of increasing partial pressures of CO₂corresponding to 5.66 and 8.33% CO₂ caused reversible fluorescencechanges as documented in FIG. 9.

EXAMPLE 7

[0099] Fifty mg of a pH sensitive copolymer composed ofN,N-Dimethylacrylamide and N-tert-butylacrylamide monomers with acovalently linked 4-acrylamidofluorescein was dissolved into 1 ml of THFin the manner described by Alder et al. in the above-referenced patentapplication WO 95/30148. The polymer solution was striped at a speed of50 mm/sec and dispensed at a rate of 4 ml/sec from a nozzle head located100 m above the Mylar® film. After solvent evaporation the stripes werevirtually colorless until wetted when they became faint green with abasic aqueous sample for measurement.

EXAMPLE 8

[0100] A striped pH sensor constructed as in Example 7 was furtherplaced in the sampling device and measured with the Perkin Elmer LS50-Bin a manner similar to that described in example 6. In this case, theexcitation wavelength was set to 485 nm and emission recorded at 530 nmwhile consecutive buffer samples corresponded to pH 7.5, 7.1, 6.8, 7.1,and 7.5 were introduced to the sensor. The reversible fluorescencequenching due to acidification of the fluorescein sensor dye by thesamples is as recorded in FIG. 10.

EXAMPLE 9

[0101] Using striping methods as described in examples 3, 5 and 7, aseries of parallel sensor stripes for oxygen, carbon dioxide and pH werelaid down on a Mylar® film similar to that illustrated in FIG. 1. A 150m thick film of Mylar® with double sided adhesive backing giving a totalthickness of 210 m was punched with a series of parallel cutoutstransverse to the longitudinal direction of the film to formintermediate web 26. This intermediate web was then fixed to a clearfilm of Mylar® to form cover web 28, and a series of holes punched, oneat each end of the parallel cutouts. In the final assembly step, thefilm containing the sensor stripes was placed as the last sandwich layeron the bottom with the sensor side in contact with the transversecutouts on the intermediate layer as shown in FIG. 4, thus formingsample chambers 118 approximately 210 m deep. For measurements andanalyte determinations, this sensor assembly was subsequently placed inan instrument having several fiber optic splitter assemblies arranged inparallel with the sample chambers. The appropriate color excitation andcollection optic was located directly below the corresponding stripe tobe measured as indicated in FIG. 5. As the assembly containing thesensor stripes and sample chambers was moved along, a bar containing aninlet and exit port was clamped over the portal holes in the top clearMylar® film (cover web 28) and an individual sample chamber was filledwith a single calibrant or sample. For demonstration purposes, ampuledvials of the Certain® Plus standards by Chiron Diagnostics served asboth calibrants and samples with known values. These were opened andaspirated into the sample wells over the sensor stripes. The values forlevel 1 corresponded to pH 7.151, pCO2 68.9 mmHg and pO2 69.0 mmHg. Thevalues for level 3 corresponded to pH 7.409, pCO2 40.1 mmHg and pO2104.5 mmHg. The simultaneous response of the sensors to a change incalibrant is illustrated in FIG. 11.

EXAMPLE 10

[0102] Using the sensor format and methodology described in example 9, astandard response curve was obtained for a single sensor calibrated bythree known Certain® Plus standards corresponding to 71.6, 107.7 and144.5 mm Hg oxygen and is represented by the solid line shown in FIG.12. The optical sensor assembly was then advanced to a new position andanother different but known sample aspirated onto a fresh position oneach sensor stripe. These are represented by the single sensor pointresponses. Table 1 shows a comparison of the measured values calculatedusing the calibration algorithm. Although the calibration was performedfor one sensor, the algorithm was applied to separate individual sensorpositions along the stripe, each with only a single measurement. TABLE 1Actual Level pO₂, (mmHg) 71.6 107.7 144.5 Measured Values with 73.4113.9 142.6 Individual Sensors 74.3 110.6 133.1 101.8 156.3 Average 73.9107.3 144.0

[0103] The foregoing description is intended primarily for purposes ofillustration. Although the invention has been shown and described withrespect to an exemplary embodiment thereof, it should be understood bythose skilled in the art that the foregoing and various other changes,omissions, and additions in the form and detail thereof may be madetherein without departing from the spirit and scope of the invention.

Having thus described the invention, what is claimed is:
 1. An opticalsensor adapted for sensing analyte content of a plurality of samples,said optical sensor comprising: a substrate web of predetermined length,said substrate web being substantially gas impermeable and opticallytransparent in a predetermined spectral range; a plurality of elongatedsensor stripes extending in parallel, spaced relation along the lengthof said web; each one of said plurality of sensor stripes adapted forproviding an optically discernible response to presence of at least oneanalyte; said optical sensor adapted for selective analyte-sensingcontact with the plurality of samples, wherein each one of the pluralityof samples are selectively superimposable with each one of saidplurality of elongated sensor stripes at one of a plurality of discretesample positions along the lengths thereof; said optically discernibleresponse being substantially identical at said plurality of discretesample positions.
 2. The optical sensor as set forth in claim 1, whereinthe plurality of samples comprises at least one unknown sample and atleast one calibration sample, said optical sensor adapted for beingcalibrated upon disposition of the calibration sample in saidanalyte-sensing contact with said optical sensor at at least one of saidplurality of discrete sample positions distinct from that of said atleast one unknown sample.
 3. The optical sensor as set forth in claim 1,wherein each one of said plurality of sensor stripes exhibits saidoptically discernible response in presence of incident light of apredetermined spectral range.
 4. The optical sensor as set forth inclaim 1, further comprising a multiple single use device, wherein eachone of said discrete sample positions along the lengths of said sensorstripes is adapted for analyte-sensing contact with a single one of theplurality of samples.
 5. The optical sensor as set forth in claim 1,wherein the sample is a fluid and said analyte-sensing contact comprisessurface-to-surface contact of the fluid with said sensor stripes.
 6. Anoptical sensor assembly adapted for sensing analyte content of aplurality of samples, said optical sensor assembly comprising: theoptical sensor as set forth in claim 1; at least one sample chambersuperimposable with each of said plurality of elongated sensor stripesat one of said plurality of discrete sample positions along the lengthsthereof; wherein said at least one sample chamber is adapted foralternately maintaining individual ones of the plurality of samples insaid analyte-sensing contact.
 7. The optical sensor assembly as setforth in claim 6, wherein said at least one sample chamber comprises: anelongated cavity disposed within a chamber member, said elongated cavitybeing defined by a substantially concave surface of said chamber member;said elongated cavity including first and second apertures disposed atopposite ends thereof to facilitate alternate entry and exit of theindividual ones of the plurality of samples to and from said samplechamber; said chamber member adapted to extend across said plurality ofsensor stripes with said substantially concave surface facing said web,wherein said optical sensor effectively closes said substantiallyconcave surface to define a longitudinal side wall of said elongatedcavity.
 8. The optical sensor assembly as set forth in claim 7, furthercomprising a plurality of said sample chambers.
 9. The optical sensorassembly as set forth in claim 7, wherein said at least one samplechamber is moveable for selective superimposition with said plurality ofdiscrete sample positions along the lengths of said sensor stripes. 10.The optical sensor assembly as set forth in claim 9, wherein said atleast one sample chamber is adapted to extend orthogonally to each ofsaid plurality of elongated sensor stripes.
 11. An optical sensorassembly adapted for sensing analyte content of a plurality of samples,said optical sensor assembly comprising: the optical sensor as set forthin claim 1; a plurality of sample chambers disposed in parallel, spacedrelation on said web, each one of said plurality of sample chambersbeing sealably superposed with said plurality of elongated sensorstripes at one of said plurality of discrete sample positions along thelengths thereof; wherein each of said plurality of sample chambers isadapted for alternately maintaining individual ones of the plurality ofsamples in said analyte-sensing contact.
 12. The optical sensor as setforth in claim 11, wherein the plurality of samples comprises at leastone unknown sample and at least one calibration sample, said opticalsensor adapted for being calibrated upon disposition of the calibrationsample in one of said sample chambers distinct from an other samplechamber adapted to receive said at least one unknown sample.
 13. Theoptical sensor assembly as set forth in claim 11, wherein each of saidplurality of sample chambers comprises: an elongated cavity disposedwithin a chamber member, said elongated cavity being defined by asubstantially concave surface of said chamber member; said elongatedcavity including first and second apertures disposed at opposite endsthereof to facilitate alternate entry and exit of at least an individualone of the plurality of samples to and from said sample chamber; saidchamber member sealably superposed with said substrate web and saidplurality of sensor stripes, wherein a discrete portion of said opticalsensor effectively closes said substantially concave surface to define alongitudinal side wall of said elongated cavity.
 14. The optical sensorassembly as set forth in claim 13, wherein said chamber member furthercomprises: a chamber web sealably superposed with said substrate web andsaid sensor stripes; a cover web sealably superposed with said chamberweb; said chamber web having a plurality of slots extending in spacedparallel relation across said sensor stripes; wherein each said slot andeach portion of said cover web superposed therewith define said concavesurface.
 15. The optical sensor assembly as set forth in claim 14,wherein said entry and exit apertures are disposed in said cover web.16. The optical sensor assembly as set forth in claim 14, wherein saidentry and exit apertures are disposed in said substrate web.
 17. Theoptical sensor assembly as set forth in claim 14, wherein at least oneof said entry and exit apertures is disposed in said substrate web andat least one of said entry and exit apertures is disposed in said coverweb.
 18. The optical sensor assembly as set forth in claim 13, whereinsaid plurality of sample chambers are disposed in fixed relation on saidoptical sensor.
 19. A method of operating an optical sensor, comprisingthe steps of: (a) providing an optical sensor including: i) a substrateweb of predetermined length, the substrate web being substantially gasimpermeable and optically transparent in a predetermined spectral range;ii) a plurality of elongated sensor stripes extending in parallel,spaced relation along the length of said web, each one of said pluralityof sensor stripes adapted for providing an optically discernibleresponse to presence of at least one of a plurality of discreteanalytes; iii) said optical sensor adapted for selective analyte-sensingcontact with the plurality of samples, wherein each one of the pluralityof samples are selectively superimposable with each one of saidplurality of elongated sensor stripes at one of a plurality of discretesample positions along the lengths thereof; iv) said opticallydiscernible response being substantially identical at said plurality ofdiscrete sample positions along the length thereof; v) wherein theplurality of samples comprises at least one unknown sample and at leastone calibration sample, the optical sensor adapted for being calibratedupon disposition of the calibration sample in said analyte-sensingcontact with said optical sensor at one of said discrete samplepositions distinct from that of said at least one unknown sample; (b)placing the calibration sample in said analyte-sensing contact with theoptical sensor at one of said plurality of discrete sample positionsalong the lengths of the sensor stripes; (c) measuring optical responseof the optical sensor at the one of the plurality of discrete samplepositions; (d) obtaining calibration data utilizing the optical responseof the one of the plurality of discrete sample positions; (e) placingthe at least one unknown sample in said analyte-sensing contact with theoptical sensor at another of the plurality of discrete sample positionsalong the lengths of the sensor stripes; (f) measuring optical responseof the other of the plurality of discrete sample positions; (g)utilizing the calibration data obtained for the one of the pluralitydiscrete sample positions for calibration of the optical response of theother of the plurality of discrete sample positions.
 20. The method asset forth in claim 19, wherein said step of utilizing (g) furthercomprises calculating presence and concentration of an analyte disposedin the at least one unknown sample.
 21. The method as set forth in claim19, wherein said steps of: placing (b) and measuring (c) are undertakensubstantially simultaneously with said steps of placing (e) andmeasuring (f), respectively.
 22. The method as set forth in claim 19,wherein said step of placing (e), further comprises the step of placingthe at least one unknown sample in said analyte-sensing contact with theoptical sensor adjacent the at least one of the plurality of discretesample positions.
 23. The method as set forth in claim 19, wherein: saidstep of placing (b) includes placing a calibration sample at apredetermined number of the plurality of discrete sample positions alongthe lengths of said sensor stripes; and said step of obtaining (d)includes obtaining calibration data utilizing the optical response ofthe predetermined number of the plurality of discrete sample positions.24. The method as set forth in claim 19, wherein: said step of placing(b) includes placing a calibration sample at at least two of theplurality of discrete sample positions along the lengths of the sensorstripes, the two being disposed on opposite sides of the other of theplurality of discrete sample positions along the lengths of the sensorstripes; and said step of obtaining (d) includes obtaining calibrationdata utilizing the optical response of the two of the plurality ofdiscrete sample positions along the lengths of the sensor stripes forcalibration of the optical response of the other of the plurality ofdiscrete sample positions along the lengths of the sensor stripes. 25.The method as set forth in claim 19, further comprising the steps of:placing other ones of the plurality of samples in analyte-sensingcontact with other ones of the plurality of discrete sample positionsalong the lengths of the sensor stripes, proximate the at least one ofthe plurality of discrete sample positions; measuring optical responseof the other ones of the plurality of discrete sample positions; andutilizing the calibration data obtained for the at least one discretesample position for calibration of the optical response of the otherones of the plurality of discrete sample positions.
 26. The method asset forth in claim 25, wherein: said step of placing (b) includesplacing a calibration sample at a predetermined number of the pluralityof discrete sample positions along the lengths of said sensor stripes;and said step of obtaining (d) includes obtaining calibration datautilizing the optical response of the predetermined number of theplurality of discrete sample positions.
 27. The method as set forth inclaim 19, wherein: said step of providing (a) includes providing anoptical sensor assembly including the optical sensor, a plurality ofsample chambers superimposed in parallel, spaced relation on said weband being superimposed with said plurality of elongated sensor stripesat a plurality of discrete sample positions along the lengths thereof,wherein each of the plurality of sample chambers is adapted foralternately maintaining individual ones of the plurality of samples insaid analyte-sensing contact; said step of placing (b) includes placinga calibration sample in a first one of the plurality of sample chambers;said step of measuring (c) includes measuring optical response of theoptical sensor at the first one of the plurality of sample chambers;said step of placing (e) includes placing an unknown sample in a secondone of the plurality of sample chambers, the second one of the pluralityof sample chambers being disposed adjacent the first one of theplurality of sample chambers; said step of measuring (f) includesmeasuring optical response of the optical sensor at the second one ofthe plurality of sample chambers; and said step of utilizing (g)includes utilizing the calibration data obtained from the first one ofthe plurality of sample chambers for calibration of the optical responseobtained from the second one of the plurality of sample chambersdisposed adjacent thereto.
 28. The method as set forth in claim 27,wherein: said step of placing (b) includes placing a calibration sampleat a plurality of first ones of the plurality of sample chambers; andsaid step of obtaining (d) includes obtaining calibration data utilizingthe optical response of the plurality of first ones of the plurality ofsample chambers.
 29. The method as set forth in claim 27, wherein: saidstep of placing (b) includes placing a calibration sample at at leasttwo of a plurality of first ones of the plurality of sample chambers,the at least two being disposed on opposite sides of a second one of theplurality of sample chambers; and said step of obtaining (d) includesobtaining calibration data utilizing the optical response of the atleast two of a plurality of first ones for calibration of the opticalresponse of the second one of the plurality of sample chambers.
 30. Themethod as set forth in claim 29, wherein said step of placing (b)includes placing a calibration sample at at least two sample chambersdisposed on opposite sides and adjacent a second one of the plurality ofsample chambers.
 31. The method as set forth in claim 27, wherein saidsteps of placing (b) and measuring (c) are undertaken substantiallysimultaneously with said steps of placing (e) and measuring (f),respectively.
 32. The method as set forth in claim 27, wherein: saidstep of placing (b) further includes placing a calibration sample ineach of a plurality of first ones of the plurality of sample chambers;said step of measuring (c) further includes measuring optical responseof the optical sensor at each of the plurality of first ones of theplurality of sample chambers; said step of placing (e) further includesplacing an unknown sample in respective second ones of the plurality ofsample chambers, each of said second ones of the plurality of samplechambers being disposed adjacent one of said first ones of saidplurality of sample chambers; said step of measuring (f) furtherincludes measuring optical response of the optical sensor at each of theplurality of second ones of said plurality of sample chambers; and saidstep of utilizing (g) further includes utilizing the calibration datafrom each of the first ones to analyze the optical response of thesecond ones of the plurality of sample chambers disposed adjacentthereto.
 33. The method as set forth in claim 32, wherein said steps ofplacing (b) and measuring (c) are undertaken substantiallysimultaneously, respectively, with the steps of placing (e) andmeasuring (f), for each pair of adjacent first ones and second ones.